Chevrolet Optra 2004 Owner's Manual page 33

And you would be less likely to slide under the lap belt.
If you slid under it, the belt would apply force at your
abdomen. This could cause serious or even fatal
injuries. The shoulder belt should go over the shoulder
and across the chest. These parts of the body are
best able to take belt restraining forces.
The safety belt locks if there is a sudden stop or a
crash, or if you pull the belt very quickly out of
the retractor.
CAUTION:
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You can be seriously hurt if your shoulder belt
is too loose. In a crash, you would move
forward too much, which could increase injury.
The shoulder belt should fit against your body.
To unlatch the belt, just push the button on the buckle.
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